lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
Open Source and information security mailing list archives
| ||
|
Date: Sun, 28 Feb 2016 21:28:50 -0800 From: Andy Lutomirski <luto@...nel.org> To: x86@...nel.org Cc: linux-kernel@...r.kernel.org, Borislav Petkov <bp@...en8.de>, Oleg Nesterov <oleg@...hat.com>, Andrew Cooper <andrew.cooper3@...rix.com>, Brian Gerst <brgerst@...il.com>, Andy Lutomirski <luto@...nel.org> Subject: [PATCH 05/10] x86/traps: Clear TIF_BLOCKSTEP on all debug exceptions The SDM says that debug exceptions clear BTF, and we need to keep TIF_BLOCKSTEP in sync with BTF. Clear it unconditionally and improve the comment. I suspect that the fact that kmemcheck could cause TIF_BLOCKSTEP not to be cleared was just an oversight. Signed-off-by: Andy Lutomirski <luto@...nel.org> --- arch/x86/kernel/traps.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c index dd2c2e66c2e1..19e6cfa501e3 100644 --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -598,6 +598,13 @@ dotraplinkage void do_debug(struct pt_regs *regs, long error_code) dr6 &= ~DR6_RESERVED; /* + * The SDM says "The processor clears the BTF flag when it + * generates a debug exception." Clear TIF_BLOCKSTEP to keep + * TIF_BLOCKSTEP in sync with the hardware BTF flag. + */ + clear_tsk_thread_flag(tsk, TIF_BLOCKSTEP); + + /* * If dr6 has no reason to give us about the origin of this trap, * then it's very likely the result of an icebp/int01 trap. * User wants a sigtrap for that. @@ -612,11 +619,6 @@ dotraplinkage void do_debug(struct pt_regs *regs, long error_code) /* DR6 may or may not be cleared by the CPU */ set_debugreg(0, 6); - /* - * The processor cleared BTF, so don't mark that we need it set. - */ - clear_tsk_thread_flag(tsk, TIF_BLOCKSTEP); - /* Store the virtualized DR6 value */ tsk->thread.debugreg6 = dr6; -- 2.5.0
Powered by blists - more mailing lists